Priming before wallpapering is needed on any wall that absorbs, dusts or absorbs unevenly: bare plasterboard, new plasterwork, repaired patches and a wall from which old wallpaper has just been removed. A painted wall in good condition that does not absorb usually needs no primer, but it does need a paste that bonds to a non-absorbent surface.
The purpose is different from paint: under wallpaper, the primer makes sure the paste does not get drawn away before the strip is properly in place.
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Why do you prime a wall before wallpapering?
Wallpaper paste consists largely of water: according to the product data sheet, Intervos M5 transparent non-woven paste has a dry-matter content of about 8%. If you put that kind of paste on a wall that absorbs strongly, the substrate draws the water out straight away. The paste then turns stiff before the strip is in place, and where it dries too fast, the wallpaper bonds less well.
A primer does two things. It evens out the absorbency across the whole wall, and it binds dust or a lightly powdering layer, so that the paste bonds to the wall and not to a thin layer of powder.
On the data sheets for its non-woven pastes, Intervos states that the substrate must be clean, sound, flat and only slightly absorbent, and that strongly absorbent substrates are first pre-treated with an impregnating primer. That is exactly what priming does. It is also one of the four conditions for a wall that is ready to be wallpapered.
Which walls do you need to prime before wallpapering?
That depends on the substrate. Situation by situation, it looks like this:
If you are unsure whether your wall absorbs, do the water test: spray a little water on the wall. If the spot quickly turns dark, it absorbs. Whether a wall dusts, you see with the wipe test, which you also use for priming before painting.
Plasterboard has one more factor. The paper facing of the board goes soft when it gets a lot of moisture, and you want to avoid that both when hanging and when removing later. That is why plasterboard walls need extra attention, even when renovation fleece goes onto the plasterboard.
Which primer do you use under wallpaper, and how long must it dry?
Under wallpaper you use a transparent water-based primer that regulates absorbency and fixes the substrate. Opaque wall paint is not a primer: it forms a closed layer and turns the wall into a non-absorbent surface.
How much you dilute the primer depends on the wall. For its Sigmafix Universal primer, Sigma states that it can be diluted up to 1 part to 4 parts water, and is used undiluted on strongly absorbent substrates.
The drying time is also on the data sheet. For Sigmafix Universal, Sigma gives about 2 hours until dust-dry and about 6 hours until it can be overpainted, at 23 °C and 50% humidity. If you wallpaper on a primed wall, wait until the layer is really dry. In a cold or damp room it takes longer.
Also pay attention to the room itself. For its pastes, Intervos specifies not to apply below 5 °C or above 70% humidity. In a new-build home that is no detail, because there the walls are still releasing construction moisture.
Isn’t priming unnecessary if the paste goes on the wall anyway?
No, with non-woven wallpaper and renovation fleece it is exactly the other way round. With non-woven wallpaper you roll the paste onto the wall and lay the dry strip into it. If the wall absorbs strongly, the paste has already partly been drawn away before the strip is in place. You then have less time to slide the strip and butt the seams tightly together.
Do not expect a primer to fix a bad wall either. It does not make a wall flatter and does not stick down loose paint. Holes, protruding joints and loose layers are repaired first. And if old wallpaper has just come off, first remove all the paste residue left by the wallpaper from the wall. Only then does priming make sense.
If there is spachtelputz (textured render) on the wall, priming does not remove the grain; wallpapering over spachtelputz needs its own approach.
Who assesses your wall and gets it ready for wallpaper?
At Bouwsector België our own tradespeople do that: 40 wallpaper hangers and 32 plasterers, from a team of 97 permanent tradespeople. They assess for each wall whether the substrate absorbs, dusts or needs repair, before any paste goes on.
In your request, mention what is on your walls: bare plasterboard, new plasterwork or a wall from which wallpaper has just been removed. The preparation is then already in the free quote you receive within 24 hours. During the site visit we check for each wall whether it absorbs or dusts, and what it needs is then included in the final price.
If we then wallpaper with renovation fleece, it costs from €14.99 per m², including sanding, hanging, filling and one coat of paint. After that, the wallpapering work runs as always: hanging, filling and painting.
Prices exclude VAT: 6% for a home over 10 years old, otherwise 21%.
By the Bouwsector België team, 97 in-house tradespeople · reviewed by